Connected: An Internet Encyclopedia
Domain Name Service (DNS)

Top: Connected: An Internet Encyclopedia
Up: Topics
Up: Functions

Search: |  | Search Depth: |
Search Type: | String RegEx | Search Options: | NoCase WholeWord

### Domain Name Service (DNS)

Domain naming, and its most visible component, the Domain Name Service (DNS), is critical to the operation of the Internet. The average American phone number, with area code, is 10 digits in length and encodes `10^10`, or `10,000,000,000` possibilities. The Internet IP address, at 32 bits, encodes `2^32` or `4,294,967,296` possibilities. For human engineering purposes, how can we build an effective directory of these difficult large numbers?

The telephone company solves this problem with lots of large paper directories, and operators you call and ask about numbers not in your directory. Internet solves this problem with a hierarchy of simple, mnenomic names, called domain names. Instead of remembering `205.216.138.22`, all I need to know is the host's domain name - `ns.adnc.com`. Some people think the dots in a domain name correspond to the dots in the numeric address. This is not the case. There are always three periods in an IP address, seperating its four constituent bytes. There are a variable number of periods in a domain name.

The crucial DNS documentation is provided in RFC 1034 and RFC 1035. The Encyclopedia's Programmed Instruction Course has a DNS Section, and the Encyclopedia's software section has a Dig page, discussing use of this free software diagnostic tool. DNS also plays an important role in Internet mail delivery.

- Name Servers
  - Primary and Secondary Name Servers
  - Recursion, Caching, and Authoritative Replies
- DNS Protocol Overview
  - DNS Lookups
  - Zone Transfers
  - Lower-Level Transport
- Resource Records (RRs)
  - Address (A) RRs
  - Canonical Name (CNAME) RR
  - Pointer (PTR) RR
  - Start of Authority (SOA) RR
  - Name Server (NS) RR
- Theory of Operation

Connected: An Internet Encyclopedia
Domain Name Service (DNS)